Will the femtosecond laser revolutionize corneal surgery?

On a quest to improve precision and success of corneal surgery

It seems many technologies are developed for one application but then become effectively applied for another. With laser technology there is an old witticism that "the laser is a solution looking for a problem!" This has proven to be the case with the femtosecond laser. First conceived for cutting vitreous membranes, then developed as a very successful tool for flap creation in LASIK, the femtosecond laser is now proving to be the single biggest innovation in corneal surgery in more than 30 years.

Corneal surgery has largely remained unchanged since the early 1970s when operating microscopes and 10-0 nylon sutures were introduced. Since that time, we've learned more about managing the induced astigmatism of penetrating keratoplasty (PKP) with corneal topography to guide us in suture manipulation, but the surgical techniques haven't changed much. In an era of outpatient microsurgery with less invasive procedures and faster rehabilitation in cataract, vitreoretinal, and glaucoma surgery, PKP still has slow recovery of vision with high amounts of regular and irregular astigmatism.

Certainly there have been attempts to move the techniques forward. Barraquer first described a shaped PKP in the 1950s to make corneal transplants more effective. The idea was abandoned, however, because the technique was cumbersome. In 2003, Busin resurrected the idea of a "Top Hat" shaped corneal graft using more modern surgical trephines. His studies found that using this configuration meant quicker wound healing, less wound leakage and less induced astigmatism. Still, the technique was technically challenging to perform manually and failed to garner many advocates.

Today, it's a different story. We have the first opportunity in years to move corneal transplantation forward. By harnessing the precision and flexibility of the femtosecond laser, we are able to create an almost infinite variety of cuts that can enable us to improve the precision and success of corneal surgery. These innovations will allow corneal surgeons to speed recovery, make a secure incision and provide a better quality of vision to our patients.

Evolution of the femtosecond laser

Figure 1: IntraLase laser.

In the spring of 2004, we started working in the laboratory here at the University of California, Irvine, USA to determine if it was feasible to use the IntraLase FS femtosecond laser in corneal surgery. Part of this involved looking at different cut patterns that could be used to fashion the donor cornea. This work resulted in the development of hardware and software changes to the femtosecond laser to make these cuts and the creation of IntraLase-enabled keratoplasty.

Figure 2: The ZigZag shaped incision creates a smooth corneal contour immediately after surgery with less distortion of the corneal optics and less astigmatism. (Image courtesy of Roger F. Steinert, MD)

Following FDA clearance in September 2005, Frank Price, MD, in Indianapolis, performed the first human surgery in November of the same year using the "Top Hat" configuration. Shortly after this, William Culbertson, MD and other corneal surgeons at Bascom Palmer Eye Institute began working with this modified laser, treating a variety of corneal diseases. Early in 2006, the clinical investigation expanded to Europe where it was first evaluated by Lucio Buratto, MD (Italy), Rudy Nuijts, MD (The Netherlands) and Professor Thomas Neuhann (Germany). To date more than 100 procedures have been performed globally with a variety of shaped incisions all created by the IntraLase FS laser. Meanwhile, work also continued here in Irvine to identify the most optimally shaped incisions for corneal procedures. Currently, we are working with what we call a "ZigZag" pattern (Figure 1), which is showing great promise in terms of corneal biomechanics, wound stability and healing and, in the early months, good visual results (Figure 2).

Overall, our collective experience has demonstrated an improved connection between the donor and recipient tissue, less induced astigmatism and less need to adjust or cut sutures during the healing process.